This time, it is bacteria eating arsenic. To be more precise: especially ectothiorhodospira-like purple bacteria or oscillatoria-like cyanobacteri are using arsenite as an energy source. The light-dependent oxidation of arsenite [As(III)] to arsenate [As(V)] occurrs under anoxic conditions. The recently discovered bacteria from oxygen-free hot springs in Mono Lake, California, suggest that the arsenic metabolism / photosynthesis evolved at the same time, or even before, ‘normal’ photosynthesis.

We just should not add nano-size rust particles to their food. Arsenic binds particularly well to iron oxides, or rust, and can be consequently easily removed by nano-size rust particles. Such particles can be easily produced by simmering (olive/oleic) oil and rust in a frying pan, which might be a cheap way to remove arsenic from drinking water, which presence there is still a very big problem in Bangladesh or West Bengal (and it seems also in Cornwall, UK). The clumped together arsenic and rust can be easily removed with a magnet.

Young gentoo penguins on Peterman Island (c) Wikipedia

Discussing arsenic in food and drinking water brings us consequently also to end-product of digestion. And penguins, in particular Gentoo penguins. Both together are the main source of arsenic accumulation in Antarctic soil. The droppings of this type of penguin contained far more arsenic than those of other species, such as the droppings of the southern giant petrel and up to three times more than the local seals. Consequently, the sediments of other Antarctic islands without resident penguins (but similar geology) contain half the levels of arsenic compared with sediment sampled on Ardley Island, where these penguins live. Since arsenic is present in the water, which is absorbed by krill and then accumulates in the food chain, passing to predators such as penguins, the arsenic levels measured in Antarctic soil can be used as an indicator of past (Gentoo) penguin populations: the more arsenic, the more penguins.

Marianne Mödlinger

Marianne Mödlinger is a prehistoric archaeologist. Her main research interests include Bronze Age studies, the manufacture and usage of Bronze Age arms and armour, archaeometallurgy of copper alloys, and experimental archaeology.